JP7211669B2 - Electrolytic copper foil capable of preventing tearing or wrinkling defects, electrode containing the same, secondary battery containing the same, and manufacturing method thereof - Google Patents

Description

The present invention relates to an electrodeposited copper foil with optimized Valley Mean Roughness (VMR) to prevent tearing or wrinkling, an electrode containing the same, a secondary battery containing the same, and a method for producing the same. .

A secondary battery is a type of energy conversion device that converts electrical energy into chemical energy, stores it, and converts the chemical energy back into electrical energy to generate electricity when electricity is needed. It is used as an energy source for electric vehicles as well as portable home appliances such as Secondary batteries are also called rechargeable batteries in that they can be recharged.

Secondary batteries that have economic and environmental advantages over disposable primary batteries include lead-acid batteries, nickel-cadmium secondary batteries, nickel-hydrogen secondary batteries, and lithium secondary batteries.

In particular, a lithium secondary battery can store a large amount of energy relative to its size and weight compared to other secondary batteries. Therefore, lithium secondary batteries are preferred in the field of information communication equipment where portability and mobility are important, and their application range is expanding to energy storage devices for hybrid and electric vehicles.

Lithium secondary batteries are repeatedly used in cycles of charging and discharging. When operating some device with a fully charged lithium secondary battery, the lithium ion secondary battery should have high charge/discharge capacity in order to increase the operating time of the device. Therefore, there is a continuous demand for research to meet the increasing needs of consumers for the charge/discharge capacity of lithium secondary batteries.

Such a secondary battery includes a negative electrode current collector made of copper foil, and among copper foils, electrolytic copper foil is widely used as the negative electrode current collector of the secondary battery. As the demand for secondary batteries increases and the demand for secondary batteries with high capacity, high efficiency and high quality increases, there is a demand for an electrolytic copper foil that can improve the characteristics of secondary batteries. In particular, there is a demand for an electrolytic copper foil that can ensure high capacity secondary batteries and stable capacity maintenance.

As the thickness of the electrodeposited copper foil becomes thinner, the amount of active material that can be contained in the same space increases and the number of current collectors increases, thereby increasing the capacity of the secondary battery. However, the thinner the electrodeposited copper foil, the more curling occurs, and defects such as tearing or wrinkling of the electrodeposited copper foil occur due to the curling of the edge portion when the electrodeposited copper foil is wound. Therefore, it is difficult to manufacture and use a very thin film type electrodeposited copper foil. Therefore, in order to manufacture an electrodeposited copper foil having a very thin thickness, curling of the electrodeposited copper foil should be prevented.

In addition, the electrodeposited copper foil should not be torn or wrinkled during the manufacturing process of the secondary battery electrode or the secondary battery using the electrodeposited copper foil. In particular, in the process of manufacturing an electrodeposited copper foil or a secondary battery electrode using the electrodeposited copper foil by a roll-to-roll (RTR) process, the electrodeposited copper foil is removed during the winding process or the coating process of the active material. Defects such as corner tearing should not occur.

Accordingly, the present invention relates to an electrodeposited copper foil, an electrode including the same, a secondary battery including the same, and a method for manufacturing the electrodeposited copper foil that can satisfy the limitations and requirements of the related art as described above.

An embodiment of the present invention seeks to provide an electrodeposited copper foil that does not curl, wrinkle, or tear during the manufacturing process even though it has a small thickness. In addition, an embodiment of the present invention provides an electrode for a secondary battery using the electrodeposited copper foil or an electrodeposited copper foil that does not curl, wrinkle, or tear during the manufacturing process of the secondary battery.

Another embodiment of the present invention seeks to provide a secondary battery electrode including such an electrolytic copper foil, and a secondary battery including such a secondary battery electrode.

Yet another embodiment of the present invention seeks to provide a method for manufacturing an electrolytic copper foil that prevents curling, wrinkling, or tearing.

In addition to the aspects of the invention described above, other features and advantages of the invention are set forth below or may be apparent from such description to those of ordinary skill in the art to which the invention pertains. would get.

According to one aspect of the present invention as described above, comprising a copper layer and having a Valley Mean Roughness of 0.8-12.5, a (220) plane texture coefficient of 0.49-1.28 [ TC(220)], a tensile strength of 25 to 51 kgf/mm ² , and a widthwise weight deviation of 3% or less. The average roughness (Valley Mean Roughness) is calculated by Equation 2 below.

[Formula 1]
Width direction weight deviation (%) = (standard deviation of weight / arithmetic mean of weight) × 100

[Formula 2]
Valley average roughness VMR = [maximum valley depth Rv of roughness profile] / [surface roughness Ra]

The electrolytic copper foil may have a surface roughness of 2.5 μm or less.

The electrodeposited copper foil may have a surface roughness difference of 0.65 μm or less between both surfaces.

The electrolytic copper foil may have a thickness of 4-30 μm.

The electrolytic copper foil may include a protective layer disposed on the copper layer.

The protective layer may include at least one of chromium (Cr), a silane compound, and a nitrogen compound.

According to another aspect of the present invention, an electrodeposited copper foil; and an active material layer disposed on said electrodeposited copper foil, said electrodeposited copper foil comprising a copper layer; (220) plane texture coefficient [TC(220)] of 0.49 to 1.28; tensile strength of 25 to 51 kgf/ ^mm2 ; and width direction weight deviation of 3% or less; The width direction weight deviation is calculated by Equation 1 below, and the Valley Mean Roughness is calculated by Equation 2 below.

[Formula 1]
Width direction weight deviation (%) = (standard deviation of weight / arithmetic mean of weight) × 100

[Formula 2]
Valley average roughness VMR = [maximum valley depth Rv of roughness profile] / [surface roughness Ra]

The electrolytic copper foil of the secondary battery electrode may have a surface roughness of 2.5 μm or less.

The electrolytic copper foil of the secondary battery electrode may have a surface roughness difference of 0.65 μm or less between both surfaces.

The electrolytic copper foil of the secondary battery electrode may have a thickness of 4 to 30 μm.

The electrolytic copper foil of the secondary battery electrode may include a protective layer disposed on the copper layer.

The secondary battery electrode protective layer may include at least one of chromium (Cr), a silane compound, and a nitrogen compound.

The active material layer includes carbon; a metal of Si, Ge, Sn, Li, Zn, Mg, Cd, Ce, Ni or Fe; an alloy containing the metal; an oxide of the metal; and a composite of the metal and carbon. one or more active materials selected from the group consisting of

According to still another aspect of the present invention, a positive electrode; a negative electrode composed of the electrode for a secondary battery; an electrolyte providing an environment in which lithium ions can move between the positive electrode and the negative electrode; and a separator electrically insulating the positive electrode and the negative electrode.

According to still another aspect of the present invention, the steps of preparing an electrolytic solution; and performing electroplating using the electrolytic solution to form a copper layer, the electrolytic solution containing 70-90 g/L Copper ions, 50-150 g/L sulfuric acid, 5-45 mg/L arsenic (As), 5-25 mg/L acetamide, and 5-20 mg/L Polypropylene glycol (PPG), forming the copper layer includes applying a current density of 40 to 80 A/dm ² between electrode plates and a rotating drum spaced apart from each other in the electrolytic solution. provided.

In forming the copper layer, the electrolyte may be supplied with a flow rate deviation of 5% or less per unit minute, and the flow rate deviation per unit minute may be calculated by Equation 4 below.

[Formula 4]
Electrolytic solution flow rate deviation per unit minute (%) = [(maximum flow rate per minute - minimum flow rate per minute) / average flow rate per minute] x 100

The electrodeposited copper foil manufacturing method may further include forming a protective layer on the copper layer.

Forming the protective layer may include anticorrosion treating the surface of the copper layer using at least one of chromium (Cr), a silane compound, and a nitrogen compound.

Forming the protective layer may include immersing the copper layer in an antirust solution containing 0.5 to 1.5 g/L of chromium (Cr).

The general description of the present invention as set forth above is merely for the purpose of illustrating or explaining the present invention, and does not limit the scope of the present invention.

According to an embodiment of the present invention, curling, wrinkling, or tearing is prevented during the manufacturing process of the electrolytic copper foil. In addition, a long-life secondary battery that can maintain a high charge-discharge capacity for a long period of time despite repeated charge-discharge cycles can be manufactured. In addition, when such an electrolytic copper foil is used, curling, wrinkling, or tearing of the electrolytic copper foil is prevented during the manufacturing process of the secondary battery electrode or the secondary battery.

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with the detailed description, serve to explain the principles of the invention.
1 is a schematic cross-sectional view of an electrolytic copper foil according to one embodiment of the present invention; FIG. It is an example of a roughness profile for explaining the "maximum valley depth of roughness profile (Rv)" based on the JIS B 0601:2001 standard. It is an illustration for an XRD graph of an electrolytic copper foil. FIG. 4 is a schematic cross-sectional view of an electrolytic copper foil according to another embodiment of the present invention; FIG. 4 is a schematic cross-sectional view of a secondary battery electrode according to still another embodiment of the present invention; FIG. 4 is a schematic cross-sectional view of a secondary battery electrode according to still another embodiment of the present invention; FIG. 4 is a schematic cross-sectional view of a secondary battery according to still another embodiment of the present invention; 5 is a schematic diagram of a manufacturing process of the copper foil illustrated in FIG. 4; FIG.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

It will be obvious to those skilled in the art that various modifications and variations of the present invention are possible without departing from the spirit and scope of the present invention. Accordingly, this invention includes all modifications and variations that come within the scope of the appended claims and their equivalents.

Shapes, sizes, ratios, angles, numbers, etc. disclosed in the drawings for describing embodiments of the present invention are exemplary, and the present invention is not limited by the items shown in the drawings. Absent. The same components may be referred to by the same reference numerals throughout the specification.

Where "including," "having," "consisting," etc. are used herein, other parts may be added unless the phrase "only" is used. Where an element is referred to in the singular, it includes the plural unless expressly specified otherwise. Also, in interpreting the components, it is interpreted to include an error range even if there is no separate explicit description.

When describing a positional relationship, for example, when the positional relationship between two parts is explained by "above", "above", "below", "beside", etc., "immediately" Alternatively, one or more other parts can be positioned between the two parts unless the expression "directly" is used.

In the case of a description of a temporal relationship, for example, when the temporal context is explained by "after", "following", "next", "before", etc., "immediately" or " Non-continuous instances may be included unless the term "directly" is used.

Phrases such as “first,” “second,” etc. are used to describe various components, but these components are not limited by such terms. Such terms are merely used to distinguish one component from another. Therefore, the first component referred to below may be the second component within the spirit of the present invention.

The term "at least one" should be understood to include all possible combinations of one or more related items.

Each feature of various embodiments of the present invention can be partially or wholly combined or combined with each other, various technical interlocking and driving are possible, and each embodiment can be independent of each other They may be operable and may be implemented together in a related relationship.

FIG. 1 is a schematic cross-sectional view of an electrolytic copper foil 101 according to one embodiment of the invention.

As shown in FIG. 1 , the electrolytic copper foil 101 of the present invention includes a copper layer 111 . Copper layer 111 has a matte surface MS and an opposite shiny surface SS.

A copper layer 111 can be formed on the rotating anode drum, for example, through electroplating (see FIG. 8). At this time, the shiny surface SS refers to the surface in contact with the rotating negative electrode drum during the electroplating process, and the matte surface MS refers to the side opposite to the shiny surface SS.

Electrodeposited copper foil 101 has a first surface S1, which is the surface in the matte surface MS direction, and a second surface S2, which is the surface in the shiny surface SS direction, with copper layer 111 as a reference. Referring to FIG. 1, the first surface S1 of the electrolytic copper foil 101 is the surface of the first protective layer 112a, and the second surface S2 is the shiny surface SS. According to an embodiment of the present invention, the first protective layer 112a may be omitted, and when the first protective layer 112a is omitted, the matte surface MS of the copper layer 111 may be the first surface S1 of the electrolytic copper foil 101. Become.

The second surface generally has a lower surface roughness Rz than the first surface. However, one embodiment of the present invention is not limited to this, and the surface roughness Rz of the second surface may be the same as or higher than the surface roughness Rz of the first surface. For example, the surface roughness of the second surface may be lower or higher than the surface roughness Rz of the first surface, depending on the degree of polishing of the rotating negative electrode drum 12 (see FIG. 8) used to manufacture the copper layer 111. good. The surface of the rotating negative electrode drum 12 can be polished with a polishing brush having a grit of #800 to #3000.

Referring to FIG. 1, the electrolytic copper foil 101 includes a first protective layer 112a disposed on the matte surface MS of the copper layer 111. As shown in FIG. The first protective layer 112a may be omitted.

The protective layer 112 may be disposed on at least one of the matte surface MS and the shiny surface SS of the copper layer 111 . Referring to FIG. 1, a first protective layer 112a is disposed on the matte surface MS. However, an embodiment of the present invention is not limited to this, and the first protective layer 112a may be arranged only on the shiny surface SS, or may be arranged on both the matte surface MS and the shiny surface SS. .

The protective layer 112 can protect the copper layer 111 and prevent the copper layer 111 from being oxidized and degraded during storage or distribution. Therefore, the protective layer 112 is also called an antirust film.

According to an embodiment of the present invention, protective layer 112 may include at least one of chromium (Cr), a silane compound, and a nitrogen compound.

For example, the protective layer 112 may be made of an anti-rust solution containing chromium (Cr), ie, an anti-rust solution containing a chromate compound.

The electrolytic copper foil 101 of the present invention can have a tensile strength of 25-51 kgf/mm ² at room temperature (25±15° C.).

The tensile strength is measured using a universal testing machine (UTM), where the sample is heat-treated at 135° C. for 10 minutes before being measured. At this time, the width of the sample is 12.7 mm, the distance between grips is 50 mm, and the test speed is 50 mm/min.

When the tensile strength of the electrodeposited copper foil 101 is less than 25 kgf/mm ² , the electrodeposited copper foil 101 is easily deformed by the force applied during the roll-to-roll process of the electrode manufacturing process and/or the secondary battery manufacturing process. There is a risk of tearing and/or wrinkling. On the other hand, when the tensile strength of the electrodeposited copper foil 101 exceeds 51 kgf/mm ² , the electrodeposited copper foil 101 is likely to be torn when subjected to tension during the manufacturing process, and the workability of the secondary battery manufacturing process is reduced. descend.

The weight deviation in the width direction of the electrolytic copper foil 101 of the present invention may be 3% or less. The weight deviation in the width direction can be obtained as follows.

First, 5 cm×5 cm samples are taken from the left, center, and right points along the width of the electrodeposited copper foil 101, and the weights of the three samples are measured. Subsequently, the arithmetic mean and standard deviation of the measured values are obtained, and the weight deviation in the width direction is calculated by Equation 1 below.

[Formula 1]
Weight deviation in width direction (%) = (standard deviation of weight/arithmetic mean of weight) x 100

If the weight deviation in the width direction of the electrodeposited copper foil 101 exceeds 3%, wrinkles are generated at the portion where the weight deviation exceeds 3% in the roll-to-roll process of manufacturing the battery, thereby increasing the defect rate.

Meanwhile, according to an embodiment of the present invention, as the secondary battery is repeatedly charged and discharged, contraction and expansion of the active material layers 120a and 120b alternately occur. Separation of the copper foil 101 is induced to reduce the capacity of the secondary battery. Therefore, in order to ensure the capacity retention rate and life of the electrode above a certain level (that is, to suppress the capacity decrease of the secondary battery), the electrolytic copper foil 101 is superior to the active material. The adhesion strength between the electrolytic copper foil 101 and the active material layers 120a and 120b should be high due to the coating property.

Generally, it is known that the adhesive strength between the electrodeposited copper foil 101 and the active material layers 120a and 120b can be improved by controlling the surface roughness Rz of the electrodeposited copper foil 101. FIG. The surface roughness Rz is also referred to as ten-point average roughness. In the surface roughness profile, the surface roughness Rz is the sum (absolute value) of the five distances farthest on the upper side from the center line of the sample section, and the sum of the distances of the five farthest points on the lower side (absolute value value) and divided by 5. The surface roughness Rz can be measured according to JIS B 0601:2001 using a Mahrsurf M300 roughness meter manufactured by Mahr.

According to an embodiment of the present invention, surface roughnesses Rz1 and Rz2 of the first and second surfaces S1 and S2 of the electrolytic copper foil 101 may be 2.5 μm or less. When the surface roughnesses Rz1 and Rz2 exceed 2.5 μm, the first and second surfaces S1 and S2 of the electrolytic copper foil 101 are excessively non-uniform, resulting in poor coating uniformity of the negative active material. As a result, the adhesion between the electrolytic copper foil 101 and the first and second active material layers 120a and 120b is significantly reduced.

According to an embodiment of the present invention, a difference (|Rz1−Rz2|) between the surface roughness Rz1 of the first surface and the surface roughness Rz2 of the second surface may be 0.65 μm or less. When the difference in surface roughness between the first and second surfaces exceeds 0.65, the difference in surface roughness Rz between the first and second surfaces S1 and S2 causes the active material to , S2 are not evenly coated on both sides. Therefore, a difference in electrical and physical properties may occur between the two surfaces S1 and S2 during charging and discharging of the secondary battery, which may reduce the capacity retention rate and life of the secondary battery. For example, after active material coating, there is a difference in adhesion between the first and second active material layers 120a and 120b and the electrolytic copper foil 101 on the first and second surfaces. As a result, the electrode is bent in the direction in which the adhesive strength is large after the electrode is manufactured, thereby increasing the defect rate.

However, in practice, the specifications require that the electrodeposited copper foil 101 whose surface roughness Rz is appropriately adjusted (for example, adjusted to 2.5 μm or less) is used. does not necessarily satisfy the adhesive strength of That is, the electrodeposited copper foil 101 having a surface roughness Rz of 2.5 μm or less cannot always guarantee a secondary battery capacity retention rate of 83% or more (after 500 charge/discharge cycles) required by the industry.

In particular, when the active material layers 120a and 120b contain Si to increase the capacity of the secondary battery, the relationship between the surface roughness Rz of the electrolytic copper foil 101 and the capacity retention rate of the secondary battery is even lower. was shown.

According to one embodiment of the present invention, in ensuring the adhesion between the electrolytic copper foil 101 and the active material layers 120a and 120b that is sufficiently large enough to ensure a secondary battery capacity retention rate of 83% or more, the electrolytic copper It has been discovered that the "Valley Mean RoughnessVMR" of the foil 101 is a more important factor than the surface roughness Rz.

Hereinafter, the "valley mean roughness VMR" of the electrolytic copper foil 101 will be specifically described with reference to FIG.

The "valley average roughness VMR" is obtained by measuring the "maximum valley depth Rv of the roughness profile" and the "surface roughness Ra" of the electrolytic copper foil 101, respectively, and the "maximum valley depth Rv of the roughness profile" and It can be calculated by calculating the measured value of "surface roughness Ra" according to Equation 2 below.

[Formula 2]
Valley average roughness VMR = [maximum valley depth Rv of roughness profile] / [surface roughness Ra]

The "maximum valley depth Rv of the roughness profile" defined in the JIS B 0601:2001 standard is the deepest valley in the surface roughness profile (sampling length: 4 mm), as illustrated in FIG. ) from the mean line.

The "surface roughness Ra" defined in the JIS B 0601:2001 standard is also called arithmetic mean roughness. In the surface roughness profile, the surface roughness Ra is determined by summing the total area of the upper and lower sides of the center line of the measurement section (reference length) and dividing the sum by the length of the measurement section. .

The "maximum valley depth Rv of the roughness profile" and the "surface roughness Ra" are measured at any three points on the surface using a roughness meter manufactured by Mitutoyo Co., Ltd. according to the JIS B 0601:2001 standard. Measure the maximum valley depth Rv of the profile and the surface roughness Ra, respectively [sampling length: 4 mm, stylus tip radius: 2 μm, stylus tip taper angle : 60°, measuring force: 0.75 mN], and then calculating these average values. The roughness profile is for the surface of the electrolytic copper foil.

According to one embodiment of the present invention, the valley average roughness VMR of the roughness profile of said first and second surfaces S1, S2 is between 0.8 and 12.5.

When the valley-average roughness VMR of the roughness profiles of the first and second surfaces S1 and S2 is less than 0.8, the copper foil is Slippage occurs, tension is unevenly applied to the copper foil, and tearing occurs.

On the other hand, if the valley-average roughness VMR of the roughness profiles of the first and second surfaces S1 and S2 exceeds 12.5, a portion having a high valley-average roughness VMR is formed as a notch in the manufacturing process of the secondary battery. It acts and tears occur.

According to one embodiment of the present invention, the matte surface MS and the shiny surface SS of the copper layer 111 have crystallographic planes, and the (220) plane texture coefficient [TC (220)] is between 0.49 and 1.28.

More specifically, the copper layer 111 has a plurality of crystal planes, and the crystal planes can be expressed using a Miller index. Specifically, the crystal plane of the copper layer 111 may be represented by the (hkl) plane. Each such crystal face has a texture coefficient (TC), which can be measured or calculated using X-ray diffraction (XRD) of the crystal face.

A method for measuring and calculating the texture coefficient (TC) of the crystal plane of the copper layer 111 forming the electrolytic copper foil 101 will be described below with reference to FIG.

FIG. 3 is an illustration for an XRD graph of an electrolytic copper foil. More specifically, FIG. 3 is an XRD graph of copper layer 111 forming electrolytic copper foil 101 . Each peak in FIG. 3 corresponds to a crystal plane.

The (220) plane texture coefficient [TC(220)] can be obtained as follows.

By performing X-ray diffraction (XRD) [Target: Copper K alpha 1, 2θ interval: 0.01°, 2θ scan speed: 3°/min] in the range of diffraction angles (2θ) from 30° to 95°, An XRD graph with peaks corresponding to n crystal planes [for example, peaks corresponding to (111), (200), (220), and (311) planes (n = 4)] is obtained, and the XRD diffraction intensity [I(hkl)] of each crystal plane (hkl) is obtained from this graph. Also, the XRD diffraction intensity [I ₀ (hkl)] for each of the n crystal planes of the standard copper powder specified by JCPDS (Joint Committee on Powder Diffraction Standards) is determined. Subsequently, after calculating the arithmetic mean value of I(hkl)/I ₀ (hkl) of the n crystal planes, divide I(220)/I ₀ (220) of the (220) plane by the arithmetic mean value. Then, the (220) plane texture coefficient [TC(220)] is calculated. That is, the (220) plane texture coefficient [TC(220)] is calculated based on Equation 3 below.

[Formula 3]

A higher (220) plane texture coefficient [TC(220)] means that the copper layer 111 has a denser crystal structure. The (220) plane texture coefficient [TC(220)] of each of the matte surface MS and the shiny surface SS is preferably 0.49 or more. When the (220) plane texture coefficient [TC(220)] is less than 0.49, the crystal structure of the electrodeposited copper foil 101 is not dense, and the risk of the electrodeposited copper foil 101 being torn during the manufacturing process is high. According to one embodiment of the present invention, the (220) plane texture coefficient of the matte surface MS or shiny surface SS of the copper layer 111 is also referred to as the (220) plane texture coefficient [TC(220)] of the electrolytic copper foil 101 . In addition, according to an embodiment of the present invention, the crystal structure of the copper layer 111 can also be referred to as the crystal structure of the electrolytic copper foil 101 .

On the other hand, if the (220) plane texture coefficient [TC(220)] exceeds 1.28, the crystal structure of the copper layer 111 is too dense, so the elongation ratio is reduced to less than 3%. Easily torn in the process. In addition, since the active area with which the negative electrode active material can stably contact is insufficient, sufficient adhesive strength cannot be secured between the electrolytic copper foil 101 and the negative electrode active material. Therefore, since the electrolytic copper foil 101 does not expand and contract together with the first and second active material layers 120a and 120b when the secondary battery is charged and discharged, the first and second active material layers 120a and 120b are separated from the electrolytic copper foil 101. The risk of separation increases, and as a result, the capacity retention rate of the secondary battery decreases, making it impossible to manufacture stable products.

According to one embodiment of the present invention, the electrolytic copper foil 101 may have a thickness of 4-30 μm.

When the electrodeposited copper foil 101 is used as a current collector of an electrode in a secondary battery, the thinner the electrodeposited copper foil 101 is, the more current collectors can be accommodated in the same space, thereby increasing the capacity of the secondary battery. It is advantageous for conversion. However, when the thickness of the electrodeposited copper foil 101 is less than 4 μm, workability is significantly reduced in the process of manufacturing secondary battery electrodes and secondary batteries using the electrodeposited copper foil 101 .

On the other hand, when the thickness of the electrodeposited copper foil 101 exceeds 30 μm, the thickness of the electrode for a secondary battery using the electrodeposited copper foil 101 is increased, and such a thickness reduces the capacity of the secondary battery. Implementation can be difficult.

FIG. 4 is a schematic cross-sectional view of an electrolytic copper foil 102 according to another embodiment of the invention. In order to avoid duplication, the description of the components already described will be omitted.

Referring to FIG. 4, an electrolytic copper foil 102 according to another embodiment of the present invention includes a copper layer 111 and first and second protective layers 112a disposed on the matte surface MS and shiny surface SS of the copper layer 111, respectively. , 112b. Compared with the electrolytic copper foil 101 shown in FIG. 1, the electrolytic copper foil 102 shown in FIG.

For convenience of explanation, of the two protective layers 112a and 112b, the protective layer 112a arranged on the matte surface MS of the copper layer 111 is called a first protective layer, and the protective layer 112b arranged on the shiny surface SS is called a first protective layer. Also referred to as 2 protective layers.

In addition, the electrolytic copper foil 102 shown in FIG. 4 has a first surface S1, which is a surface in the matte surface MS direction, and a second surface S2, which is a surface in the shiny surface SS direction, with the copper layer 111 as a reference. Here, the first surface S1 of the electrolytic copper foil 102 is the surface of the first protective layer 112a arranged on the matte surface MS, and the second surface S2 is the surface of the second protective layer 112b arranged on the shiny surface SS. be.

According to another embodiment of the present invention, each of the two protective layers 112a and 112b may include at least one of chromium (Cr), a silane compound and a nitrogen compound.

The valley average roughness VMR of the roughness profile of the first and second surfaces S1 and S2 of the electrolytic copper foil 102 shown in FIG. 4 is 0.8 to 12.5.

Electrodeposited copper foil 102 may have a (220) plane texture coefficient [TC(220)] of 0.49 to 1.28 for each of matte surface MS and shiny surface SS.

The electrolytic copper foil 102 may have a tensile strength of 25-51 kgf/mm ² at room temperature (25±15° C.).

The weight deviation in the width direction of the electrolytic copper foil 102 may be 3% or less.

The surface roughnesses Rz1 and Rz2 of the first and second surfaces S1 and S2 of the electrolytic copper foil 102 shown in FIG. 4 are 2.5 μm or less. The difference in surface roughness Rz2 (|Rz1-Rz2|) can be 0.65 μm or less.

The electrolytic copper foil 102 of FIG. 4 has a thickness of 4-30 μm.

FIG. 5 is a schematic cross-sectional view of a secondary battery electrode 103 according to still another embodiment of the present invention. The secondary battery electrode 103 shown in FIG. 5 can be applied to the secondary battery 105 shown in FIG. 7, for example.

Referring to FIG. 5, a secondary battery electrode 103 according to still another embodiment of the present invention includes an electrolytic copper foil 101 and an active material layer 120 a disposed on the electrolytic copper foil 101 . Here, the electrolytic copper foil 101 includes a copper layer 111 and a first protective layer 112a disposed on the copper layer 111, and is used as a current collector.

Specifically, the electrolytic copper foil 101 has a first surface S1 and a second surface S2, and the active material layer 120a is disposed on at least one of the first surface S1 and the second surface S2 of the electrolytic copper foil 101. be. An active material layer 120a may be disposed on the first protective layer 112a.

FIG. 5 shows an example in which the electrolytic copper foil 101 of FIG. 1 is used as a current collector. However, another embodiment of the present invention is not limited to this, and the copper foil 102 shown in FIG. 4 may be used as the current collector of the secondary battery electrode 103 .

Also, FIG. 5 shows a structure in which the first active material layer 120a is disposed only on the first surface S1 of the electrolytic copper foil 101, but another embodiment of the present invention is limited thereto. Instead, the first and second active material layers 120a and 120b can be arranged on both the first surface S1 and the second surface S2 of the electrolytic copper foil 101, respectively. Also, the active material layer 120 may be arranged only on the second surface S2 of the electrolytic copper foil 101 .

The first active material layer 120a shown in FIG. 5 may be made of an electrode active material, particularly a negative electrode active material. That is, the secondary battery electrode 103 shown in FIG. 5 may be used as a negative electrode.

The active material layer 120 may include, as a negative active material, at least one of carbon; metal; alloy containing metal; oxide of metal; and composite of metal and carbon. At least one of Si, Ge, Sn, Li, Zn, Mg, Cd, Ce, Ni and Fe may be used as the metal. Specifically, the metal preferably contains silicon (Si) in order to increase the charge/discharge capacity of the secondary battery.

As the secondary battery is repeatedly charged and discharged, contraction and expansion of the active material layer 120 alternately occur, which induces separation between the active material layer 120 and the copper foil 101, thereby reducing the charge/discharge efficiency of the secondary battery. Let In particular, the active material layer 120 containing silicon (Si) expands and contracts significantly.

According to still another embodiment of the present invention, the electrodeposited copper foil 101 used as a current collector can contract and expand in response to the contraction and expansion of the active material layer 120, so that the active material layer 120 contracts and expands. Even if it expands, the electrodeposited copper foil 101 is thereby deformed and is not torn. Accordingly, no separation occurs between the electrolytic copper foil 101 and the active material layer 120a. Accordingly, a secondary battery including the secondary battery electrode 103 has excellent charge/discharge efficiency and excellent capacity retention rate.

FIG. 6 is a schematic cross-sectional view of a secondary battery electrode 104 according to still another embodiment of the present invention.

A secondary battery electrode 104 according to still another embodiment of the present invention includes an electrolytic copper foil 102 and first and second active material layers 120 a and 120 b disposed on the electrolytic copper foil 102 . Electrodeposited copper foil 102 includes copper layer 111 and first and second protective layers 112 a and 112 b disposed on both sides of copper layer 111 . However, an embodiment of the present invention is not limited thereto, and one of the first active material layer 120a and the second active material layer 120b may be omitted.

Specifically, the secondary battery electrode 104 shown in FIG. including. Here, active material layer 120a disposed on first surface S1 of electrolytic copper foil 102 is referred to as a first active material layer, and active material layer 120b disposed on second surface S2 of electrolytic copper foil 102 is referred to as a second active material layer. Also called an active material layer.

The two first and second active material layers 120a, 120b may be made of the same material and the same method, or may be made of different materials or different methods.

FIG. 7 is a schematic cross-sectional view of a secondary battery 105 according to still another embodiment of the invention. The secondary battery 105 illustrated in FIG. 7 is, for example, a lithium secondary battery.

Referring to FIG. 7, the secondary battery 105 includes a cathode 370, an anode 340, an electrolyte 350 disposed between the cathode 370 and the anode 340 to provide an environment in which ions can move, and It includes a separator 360 that electrically isolates the positive electrode 370 and the negative electrode 340 . Here, the ions that move between the positive electrode 370 and the negative electrode 340 are, for example, lithium ions. Separation membrane 360 separates positive electrode 370 and negative electrode 340 to prevent charge generated at one electrode from moving to another electrode through secondary battery 105 and being wasted. Referring to FIG. 7, separation membrane 360 is positioned within electrolyte 350 .

The cathode 370 includes a cathode current collector 371 and a cathode active material layer 372, and the cathode current collector 371 may be aluminum foil.

The negative electrode 340 includes a negative current collector 341 and a negative active material layer 342 , and an electrolytic copper foil may be used as the negative current collector 341 .

According to an embodiment of the present invention, the electrodeposited copper foils 101 and 102 disclosed in FIG. 1 or 4 may be used as the negative electrode current collector 341 . Also, the secondary battery electrodes 103 and 104 shown in FIG. 5 or 6 may be used as the negative electrode 340 of the secondary battery 105 shown in FIG.

Hereinafter, a method for manufacturing the electrolytic copper foil 102 according to one embodiment of the present invention will be specifically described with reference to FIG.

FIG. 8 is a schematic diagram of a method for manufacturing the electrolytic copper foil 102 shown in FIG.

The method of manufacturing the electrolytic copper foil 102 of the present invention includes the steps of preparing the electrolyte solution 11 and performing electroplating using the electrolyte solution 11 to form the copper layer 111 .

Specifically, in the step of preparing the electrolytic solution 11, the electrolytic solution 11 containing copper ions is first produced. Electrolytic solution 11 is contained in electrolytic bath 10 .

Subsequently, in the step of forming the copper layer 111 by performing electroplating using the electrolyte 11, the cathode plate 13 and the rotating anode drum 12, which are spaced apart from each other, are placed in the electrolyte 11 at 40 to 80 ASD. The copper layer 111 is formed on the rotating negative electrode drum 12 by performing electroplating at a current density of (A/dm ² ). The copper layer 111 is formed by the principle of electroplating.

When the current density applied between the positive electrode plate 13 and the rotating negative electrode drum 12 is less than 40 ASD, grain formation of the copper layer 111 increases, and when it exceeds 80 ASD, grain refinement is accelerated. More specifically, the current density can be adjusted to 50 ASD or higher.

The surface properties of the shiny surface SS of the copper layer 111 may vary depending on the degree of buffing or polishing of the surface of the rotating negative electrode drum 12 . In order to adjust the surface properties in the SS direction of the shiny surface, the surface of the rotating negative electrode drum 12 may be polished with a polishing brush having a grit of #800 to #3000, for example.

In the step of forming the copper layer 111, the electrolyte 11 is maintained at a temperature of 50 to 65° C., and the flow rate deviation of the electrolyte 11 is maintained at 5% or less per unit minute. At this time, the physical, chemical and electrical properties of the copper layer 111 can be controlled by adjusting the composition of the electrolyte 11 .

According to one embodiment of the present invention, the electrolyte 11 comprises 70-90 g/L copper ions, 50-150 g/L sulfuric acid, 5-45 mg/L arsenic (As), 5-25 mg/L acetamide ) and 5-20 mg/L Polypropylene glycol (PPG).

In order to facilitate the formation of the copper layer 111 by electrodeposition of copper, the concentrations of copper ions and sulfuric acid in the electrolytic solution 11 are adjusted to 70-90 g/L and 50-150 g/L, respectively. . More specifically, it is preferable to adjust the concentration of sulfuric acid in the electrolytic solution 11 to 70 to 120 g/L.

The concentration of arsenic (As) in the electrolytic solution 11 is controlled at 5-45 mg/L. However, an embodiment of the invention is not so limited.

Arsenic acts as an accelerator to accelerate the reduction reaction of copper (Cu) at a constant concentration. When the concentration of arsenic is less than 5 mg/L, the surface of the copper layer 111 is plated flat during the formation of the copper layer 111, and the valley average roughness VMR of each of the first and second surfaces of the electrolytic copper foil 102 is 0.0. less than 8.

On the other hand, when the concentration of arsenic exceeds 45 mg/L, an insoluble compound is formed when Cu2 ⁺ or ^Cu1+ , which is a copper ion, is reduced to copper (Cu), and impurities are electrodeposited (eutectoid) on the copper layer 111 together. ) can be done. Therefore, the copper layer 111 is powder-plated and the depth of the valleys increases sharply, so that the valley average roughness VMR of each of the first and second surfaces of the electrodeposited copper foil 102 reaches 12.5. will exceed. In addition, when the concentration of arsenic is high, the (311), (111) and (100) planes grow first in the process of forming the copper layer 111, and the growth of the (220) plane may be suppressed.

Therefore, in the crystal structure of the copper layer 111, the texture coefficient [TC(220)] of the (220) plane is set to 0.49 to 1.28, and the valleys of the first and second planes of the electrolytic copper foil 102 The concentration of arsenic in the electrolytic solution 11 is adjusted to 5 to 45 mg/L or less so that the average roughness VMR is 0.8 to 12.5.

The acetamide is a substance added to the electrolyte 11 to control the size of copper plating particles in the electrolyte 11 . If the size of the copper-plated particles is too small, the tensile strength of the electrolytic copper foil 102 increases, and if the size of the copper-plated particles is too large, the tensile strength of the electrolytic copper foil 102 decreases. It will be.

The concentration of the acetamide in the electrolytic solution 11 is controlled at 5-25 mg/L. However, an embodiment of the invention is not so limited.

When the concentration of acetamide exceeds 25 mg/L, the copper plating particles are ultrafinely plated, and the tensile strength of the electrolytic copper foil 102 after heat treatment exceeds 51 kgf/mm ² .

On the other hand, when the concentration of acetamide is less than 5 mg/L, the copper plating particles are coarsely plated, and the tensile strength of the electrolytic copper foil 102 after heat treatment is less than 25 kgf/mm ² .

The polypropylene glycol (PPG) is a substance added to the electrolyte to control the crystal structure of copper plating.

The higher the concentration of polypropylene glycol (PPG) in the electrolytic solution, the denser the crystal structure of the electrolytic copper foil 102, the larger the (220) plane texture coefficient. The lower the concentration, the less dense the crystal structure of the electrodeposited copper foil 102, and the smaller the (220) plane texture coefficient.

According to the invention, the concentration of polypropylene glycol (PPG) in the electrolyte is 5-20 mg/L.

If the concentration of polypropylene glycol (PPG) in the electrolytic solution is less than 5 mg/L, the crystal structure of the electrolytic copper foil 102 cannot be sufficiently developed, resulting in a (220) plane texture coefficient of less than 0.49. As described above, when the (220) plane texture coefficient is less than 0.49, the crystal structure of the electrodeposited copper foil 102 is not dense, and the risk of the electrodeposited copper foil 102 being torn during the manufacturing process is high.

On the other hand, when the concentration of polypropylene glycol (PPG) in the electrolyte exceeds 20 mg/L, the crystal structure of the electrodeposited copper foil 102 is too dense, and the (220) plane texture coefficient exceeds 1.28. It will be. As described above, when the (220) plane texture coefficient exceeds 1.28, the elongation ratio decreases to less than 3% and the film is easily torn during the manufacturing process. In addition, sufficient adhesive strength cannot be secured between the electrolytic copper foil 102 and the negative active material because the active area for stably contacting the negative active material is insufficient.

During the formation of the copper layer 111, the flow rate deviation of the electrolytic solution 11 is maintained at 5% or less per unit minute. The deviation of the flow rate of the electrolytic solution 11 is for adjusting the weight deviation of the electrolytic copper foil 102 in the width direction. The flow deviation can be determined as follows.

First, the flow rate of the electrolytic solution 11 supplied for one minute is measured at least twice. Using the measured flow rate per unit minute, the average flow rate per minute, the maximum flow rate per minute, and the minimum flow rate per minute are obtained, and the flow rate at which the electrolyte is supplied is calculated according to Equation 4 below. A deviation can be calculated.

[Formula 4]
Electrolytic solution flow rate deviation per unit minute (%) = [(maximum flow rate per minute - minimum flow rate per minute) / average flow rate per minute] x 100

In order to keep the weight deviation in the width direction of the electrolytic copper foil 102 at 3% or less, the flow rate deviation of the electrolytic solution 11 is maintained at 5% or less per unit minute. If the flow rate deviation of the electrolyte solution 11 exceeds 5%, the electrolyte solution 11 supply flow rate deviation occurs in the width direction of the electrolytic copper foil 102 . As a result, there is a difference in the efficiency of copper plating in the width direction, which causes the weight deviation of the electrolytic copper foil 102 to exceed 3%.

The copper layer 111 manufactured in this way can be cleaned in the cleaning bath 20 .

For example, acid cleaning for removing impurities on the surface of the copper layer 111, such as a resin component or a natural oxide film, and water for removing the acid solution used for the acid cleaning. Water cleaning may be performed sequentially. The washing step may be omitted.

According to an embodiment of the present invention, the method may further include forming first and second passivation layers 112a and 112b on the copper layer 111 additionally.

In the step of forming the protective layer 112, first and second protective layers 112a and 112b are formed on the copper layer 111 manufactured as described above.

Referring to FIG. 8, the copper layer 111 may be immersed in the antirust solution 31 contained in the antirust group 30 to form first and second protective layers 112a and 112b on the copper layer 111. Referring to FIG.

The rust preventive liquid 31 may include at least one of chromium (Cr), a silane compound, and a nitrogen compound.

Specifically, the rust preventive liquid 31 may contain chromium (Cr), and the chromium (Cr) may exist in the rust preventive liquid 31 in an ionic state.

The rust preventive liquid 31 may contain 0.5-1.5 g/L of chromium. The temperature of the antirust liquid 31 can be maintained at 20-40° C. for the formation of the first and second protective layers 112a, 112b. The copper layer 111 can be immersed in the antirust solution 31 for about 1 to 30 seconds.

Specifically, the manufactured copper layer 111 is immersed in an antirust solution containing 0.5 to 1.5 g/L of chromium (Cr) (for example, at room temperature for 2 to 20 seconds) and then dried. to form first and second protective layers 112a and 112b on the copper layer 111, respectively.

The rust preventive liquid may further include at least one of a silane compound and a nitrogen compound. For example, the antirust solution may contain 0.5-1.5 g/L of chromium (Cr) and 0.5-1.5 g/L of silane compounds.

The electrolytic copper foil 102 is produced by forming the protective layer 112 in this manner.

Electrodeposited copper foil 102 is then cleaned in cleaning bath 40 . Such washing steps may be omitted.

The secondary battery electrode (ie, negative electrode) of the present invention can be manufactured by coating the electrodeposited copper foil 102 of the present invention with a negative electrode active material.

The negative electrode active material is carbon; a metal of Si, Ge, Sn, Li, Zn, Mg, Cd, Ce, Ni or Fe; an alloy containing the metal; an oxide of the metal; and a composite of the metal and carbon. can be selected from the group consisting of

For example, after mixing 1 to 3 parts by weight of styrene-butadiene rubber (SBR) and 1 to 3 parts by weight of carboxymethyl cellulose (CMC) with 100 parts by weight of carbon for the negative electrode active material, distilled water is used as a solvent to form a slurry. Prepare. Subsequently, the slurry is coated on the electrodeposited copper foil 102 with a thickness of 20-100 μm using a doctor blade and pressed at 110-130° C. with a pressure of 0.5-1.5 ton/cm ² .

A lithium secondary battery can be manufactured using the secondary battery electrode (negative electrode) of the present invention manufactured by the method described above, as well as a conventional positive electrode, electrolyte, and separation membrane.

Hereinafter, the present invention will be described in detail through embodiments and comparative examples. However, the following embodiments and comparative examples are merely for helping understanding of the present invention, and the scope of the present invention is not limited by the embodiments or comparative examples.

Embodiments 1-7 and Comparative Examples 1-7

A copper layer 111 was manufactured by electroplating by applying an electric density of 60 ASD to a foil-making machine including a positive electrode plate 13 and a rotating negative electrode drum 12 which are spaced apart from each other in an electrolytic solution 11 . The electrolytic solution 11 is a copper sulfate solution. The copper ion concentration in the electrolytic solution 11 was set to 75 g/L, the sulfuric acid concentration to 100 g/L, the temperature of the electrolytic solution to 55° C., and the current density to 60 ASD. During electroplating, a circulation pump circulates the plating solution between the supply bath and the plating bath at a flow rate of 42 m ³ /hr, and fine impurities in the plating solution are removed by a Cartridg filter between the supply bath and the plating bath. bottom.

In addition, the concentration of arsenic (As), the concentration of acetamide, the concentration of polypropylene glycol (PPG) contained in the electrolytic solution 11, and the deviation of the flow rate of the electrolytic solution during plating are shown in the table below. 1.

A current density of 50 ASD was applied between the rotating negative drum 12 and the positive plate 13 to fabricate the copper layer 111 . Next, the copper layer 111 was immersed in an antirust solution for about 2 seconds to apply chromate treatment to the surface of the copper layer 111 to form the first and second protective layers 112a and 112b, thereby manufacturing the electrolytic copper foil 102. . A rust preventive solution containing chromic acid as a main component was used as the rust preventive solution, and the concentration of chromic acid was 1.0 g/L. An electrolytic copper foil was completed by immersing the copper layer formed through the electroplating in an antirust solution and then drying it.

As a result, electrolytic copper foils of Examples 1 to 7 and Comparative Examples 1 to 7 were produced.

(i) valley average roughness VMR (ii) tensile strength (iii) (220) surface texture coefficient [TC (220)] (iv) weight deviation (v) surface roughness Rz of the first and second surfaces were measured.

In addition, after manufacturing a secondary battery using an electrolytic copper foil and charging and discharging the secondary battery, (vi) the secondary battery is disassembled to check for tearing and wrinkling of the electrolytic copper foil. Observed.

(i) Valley average roughness VMR measurement Using a Mitutoyo roughness meter at three arbitrary points on the surface of the electrolytic copper foil, "maximum valley depth Rv of roughness profile" according to JIS B 0601: 2001 standard and "surface roughness Ra" respectively [sampling length: 4 mm, stylus tip radius: 2 µm, stylus tip taper angle: 60 °, measuring force ): 0.75 mN], these average values are calculated, and the measured values of the calculated “maximum valley depth Rv of the roughness profile” and “surface roughness Ra” are calculated by the following formula 2, and “ valley mean roughness VMR" can be calculated.

[Formula 2]
Valley average roughness VMR = [maximum valley depth Rv of roughness profile] / [surface roughness Ra]

(ii) Stamp strength measurement Tensile strength is measured using a universal testing machine (UTM), where the sample is measured after heat treatment at 135°C for 10 minutes. At this time, the width of the sample is 12.7 mm, the distance between grips is 50 mm, and the test speed is 50 mm/min.

(iii) (220) plane texture coefficient [TC (220)] measurement X-ray diffraction method (XRD) in the diffraction angle (2θ) range of 30° to 95° [Target: Copper K alpha 1, 2θ interval: 0.01 °, 2θ scan speed: 3°/min], an XRD graph having peaks corresponding to n crystal planes [for example, the (111) plane, (200) plane, ( 220) plane and the peak (n=4) corresponding to the (311) plane] is obtained, and the XRD diffraction intensity [I(hkl)] of each crystal plane (hkl) is obtained from this graph. Also, the XRD diffraction intensity [I ₀ (hkl) for each of the n crystal planes of the standard copper powder specified by JCPDS (Joint Committee on Powder Diffraction Standards) is determined. Subsequently, after calculating the arithmetic mean value of I(hkl)/I ₀ (hkl) of the n crystal planes, divide I(220)/I ₀ (220) of the (220) plane by the arithmetic mean value. Then, the (220) plane texture coefficient [TC(220)] is calculated. That is, the (220) plane texture coefficient [TC(220)] is calculated based on Equation 3 below.

[Formula 3]

(iv) Measurement of Weight Deviation in Width Direction Samples with a size of 5 cm×5 cm were taken from the left, center, and right points along the width direction of the electrolytic copper foil 102, and then these three samples were taken. weigh each. Subsequently, the arithmetic mean and standard deviation of the measured values are obtained, and the weight deviation in the width direction is calculated by Equation 1 below.

[Formula 1]
Weight deviation in width direction (%) = (standard deviation of weight/arithmetic mean of weight) x 100

(v) surface roughnesses Rz1 and Rz2 of the first and second surfaces and their difference (|Rz1-Rz2|)

Using a surface roughness measuring machine (M300, Mahr) according to the JIS B 0601-2001 standard, the first surface S1 and the second surface of the electrolytic copper foil 102 produced in Embodiments 1 to 7 and Comparative Examples 1 to 7 Surface roughnesses Rz1 and Rz2 of S2 were measured. Using the measurement results, the difference in surface roughness (|Rz1-Rz2|) between the first surface S1 and the second surface S2 of the electrolytic copper foil was calculated.

(vi) Observation of wrinkles and tearing

1) Production of Negative Electrode 100 parts by weight of a commercially available silicon/carbon composite negative electrode material for a negative electrode active material was mixed with 2 parts by weight of styrene-butadiene rubber (SBR) and 2 parts by weight of carboxymethyl cellulose (CMC) and distilled. A negative electrode active material slurry was prepared using water as a solvent. Using a doctor blade, the negative electrode active material slurry was applied to a thickness of 40 μm on the electrolytic copper foils of Embodiments 1 to 7 and Comparative Examples 1 to 7 having a width of 10 cm, dried at 120 ° C., and 1 ton/ A pressure of cm ² was applied to manufacture a negative electrode for a secondary battery.

2) Preparation of Electrolyte A basic electrolyte was prepared by dissolving LiPF6 as a solute at a concentration of 1M in a non-aqueous organic solvent in which ethylene carbonate (EC) and ethylmethyl carbonate (EMC) were mixed at a ratio of 1:2. A non-aqueous electrolyte was prepared by mixing 99.5% by weight of basic electrolyte and 0.5% by weight of succinic anhydride.

3) Positive Electrode Preparation Lithium manganese oxide Li1.1Mn1.85Al0.05O4 and lithium manganese oxide having an orthorhombic crystal structure o-LiMnO2 were mixed at a ratio of 90:10 (weight ratio) to prepare a positive electrode active material. bottom. A cathode active material, carbon black, and PVDF [Poly (vinylidenefluoride)] as a binder were mixed at 85:10:5 (weight ratio), and mixed with NMP as an organic solvent to prepare a slurry. . The slurry thus prepared was coated on both sides of an Al foil having a thickness of 20 μm and then dried to prepare a positive electrode.

4) Manufacture of lithium secondary battery for test A positive electrode and a negative electrode are placed inside an aluminum can so as to be insulated from the aluminum can, and a non-aqueous electrolyte and a separation membrane are placed between them to produce a coin-shaped lithium secondary battery. manufactured. The separation membrane used was polypropylene (Celgard 2325; thickness 25 μm, average pore size φ28 nm, porosity 40%).

5) Charging and discharging of secondary battery Using the lithium secondary battery manufactured in this way, the battery was driven at a charging voltage of 4.3 V and a discharging voltage of 3.4 V, and at a high temperature of 50 ° C. The battery was charged/discharged 100 times at the current rate (C-rate).

6) Presence or Absence of Wrinkles or Tearing After 100 charge/discharge cycles, the secondary battery was disassembled to observe whether wrinkles or tears occurred in the copper foil. When the copper foil was wrinkled or torn, it was indicated as "Occurrence", and when it did not occur, it was indicated as "None".

The above test results are shown in Table 2.

Referring to Tables 1 and 2, the following results can be confirmed.

The electrodeposited copper foil of Comparative Example 1, which was manufactured using an electrolyte containing a small amount of arsenic (As), had a VMR of 0.7, which was lower than the reference value, and tearing occurred. In addition, the electrodeposited copper foil of Comparative Example 2, which was manufactured using an electrolyte containing an excessive amount of arsenic (As), had a VMR of 12.7, which was larger than the reference value, and the difference in surface roughness between both surfaces (|Rz1 - Rz2| ) was also 0.66, which was larger than the reference value, and tearing occurred.

The electrodeposited copper foil of Comparative Example 3, which was manufactured using an electrolyte containing a small amount of acetamide, had a lower tensile strength than the reference value and was torn. On the other hand, the electrodeposited copper foil of Comparative Example 4, which was manufactured using an electrolyte containing an excessive amount of acetamide, had a higher tensile strength than the reference value, indicating that tearing occurred.

The electrodeposited copper foil of Comparative Example 5, which was produced with an electrolyte solution containing a small amount of polypropylene glycol (PPG), had a (220) plane texture coefficient [TC(220)] lower than the reference value, and tearing occurred. On the other hand, the electrodeposited copper foil of Comparative Example 6, which was produced using an electrolyte containing an excessive amount of polypropylene glycol (PPG), had a (220) plane texture coefficient [TC(220)] higher than the reference value, and tearing occurred.

The electrolytic copper foil of Comparative Example 7, which was produced by supplying the electrolytic solution 11 with a flow rate deviation as high as 5.3% per unit minute, had a weight deviation higher than the reference value and did not tear. A wrinkle occurred.

On the other hand, in the copper foils of Embodiments 1 to 7 according to the present invention, all numerical values were within the standard values, and wrinkles and tears did not occur.

The present invention described above is not limited by the above-described embodiments and attached drawings, and various substitutions, modifications and alterations can be made without departing from the technical scope of the present invention. It will be obvious to those who have ordinary knowledge in the technical field to which the present invention belongs. Therefore, the scope of the present invention is defined by the claims set forth below, and all changes or modifications derived from the meaning, scope and equivalents of the claims are to be included within the scope of the present invention. should be interpreted.

101, 102: copper foil 112a, 112b: first and second protective layers 120a, 120b: first and second active material layers 103, 104: secondary battery electrode MS: matte surface SS: shiny surface

Claims (18)

including a copper layer,
Valley Mean Roughness from 0.8 to 12.5;
(220) plane texture coefficient [TC(220)] between 0.49 and 1.28,
An electrolytic copper foil having a tensile strength of 25 to 51 kgf/mm ² and a weight deviation in the width direction of 3% or less;
The weight deviation in the width direction is calculated by the following formula 1,
The valley mean roughness (Valley Mean Roughness) is calculated by Equation 2 below.
[Formula 1]
Weight deviation in width direction (%) = (standard deviation of weight/arithmetic mean of weight) x 100
[Formula 2]
Valley mean roughness (VMR) = [maximum valley depth of roughness profile (Rv)]/[surface roughness (Ra)] The electrolytic copper foil according to claim 1, having a surface roughness (Rz) of 2.5 µm or less. The electrolytic copper foil according to claim 1, wherein the difference in surface roughness (Rz) between both surfaces is 0.65 µm or less. The electrolytic copper foil according to claim 1, having a thickness of 4 to 30 µm. 2. The electrolytic copper foil of claim 1, comprising a protective layer disposed on said copper layer. 6. The electrolytic copper foil of claim 5, wherein the protective layer includes at least one of chromium (Cr), a silane compound, and a nitrogen compound. an electrolytic copper foil; and an active material layer disposed on said electrolytic copper foil,
the electrolytic copper foil comprises a copper layer;
Valley Mean Roughness from 0.8 to 12.5;
(220) face texture coefficient [TC(220)] of 0.49-1.28;
A secondary battery electrode having a tensile strength of 25 to 51 kgf/mm ² and a weight deviation in the width direction of 3% or less;
The weight deviation in the width direction is calculated by the following formula 1,
The valley mean roughness (Valley Mean Roughness) is calculated by Equation 2 below.
[Formula 1]
Weight deviation in width direction (%) = (standard deviation of weight/arithmetic mean of weight) x 100
[Formula 2]
Valley mean roughness (VMR) = [maximum valley depth of roughness profile (Rv)]/[surface roughness (Ra)] 8. The secondary battery electrode according to claim 7, wherein said electrolytic copper foil has a surface roughness (Rz) of 2.5 [mu]m or less. 8. The secondary battery electrode according to claim 7, wherein the electrolytic copper foil has a surface roughness (Rz) difference of 0.65 [mu]m or less between both surfaces. 8. The secondary battery electrode according to claim 7, wherein said electrolytic copper foil has a thickness of 4 to 30 μm. The secondary battery electrode according to claim 7, wherein the electrolytic copper foil includes a protective layer disposed on the copper layer. 12. The secondary battery electrode of claim 11, wherein the protective layer includes at least one of chromium (Cr), a silane compound, and a nitrogen compound. The active material layer is
carbon;
metals Si, Ge, Sn, Li, Zn, Mg, Cd, Ce, Ni or Fe;
an alloy comprising said metal;
8. The electrode for a secondary battery according to claim 7, comprising one or more active materials selected from the group consisting of an oxide of said metal; and a composite of said metal and carbon. cathode;
A negative electrode composed of the secondary battery electrode according to any one of claims 7 to 13;
A secondary battery, comprising: an electrolyte providing an environment in which lithium ions can move between the positive electrode and the negative electrode; and a separator electrically insulating the positive electrode and the negative electrode. preparing an electrolyte; and performing electroplating using the electrolyte to form a copper layer;
The electrolytic solution is
70-90 g/L of copper ions,
50-150 g/L of sulfuric acid,
5-45 mg/L arsenic (As),
5-25 mg/L acetamide, and 5-20 mg/L Polypropylene glycol (PPG),
forming the copper layer includes applying a current density of 40 to 80 A/dm ² between an electrode plate and a rotating drum spaced apart from each other in the electrolytic solution;
In forming the copper layer,
A method for manufacturing an electrolytic copper foil, wherein the electrolytic solution is supplied at a flow rate deviation of 5% or less per unit minute;
The flow rate deviation per unit minute is calculated by Equation 4 below.
[Formula 4]
Electrolytic solution flow rate deviation per unit minute (%) = [(maximum flow rate per minute - minimum flow rate per minute) / average flow rate per minute] x 100 16. The method of claim 15, further comprising forming a protective layer on the copper layer. 17. The electrolysis of claim 16 , wherein forming the protective layer comprises anticorrosion treatment of the surface of the copper layer using at least one of chromium (Cr), a silane compound, and a nitrogen compound. Copper foil manufacturing method. 17. The electrolytic copper foil manufacturing method according to claim 16 , wherein forming the protective layer comprises immersing the copper layer in an antirust solution containing 0.5 to 1.5 g/L of chromium (Cr). Method.

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